Measuring devices, in particular a field device, for example a sensor or an actuator, as a rule may have their own operating devices or operating apparatuses for operating. These operating devices may often comprise a display device in the form of a liquid crystal display (LCD), and a plurality of buttons or switches. By means of operating device that may serve as a man-machine interface, or by means of an input/output device, the field device may make it possible for a user, operator or handler to observe, operate, configure or parameterise (parametrieren) the field device.
In industrial production in a production plant, during which production at various locations in the production sequence a sensor may need to be queried or an actuator may need to be set, it may be possible to use a plurality of field devices distributed over the production plant. However, operating this plurality of measuring devices can turn out to be difficult, because operation with the operating devices provided by the measuring device can often take place substantially only locally at the measuring device.
In order to avoid local operation, in large production plants a central control facility or control room may be used, from which a measuring device or a field device that may be located at a remote location of use can be controlled and regulated, respectively. Likewise, a measured value that may be determined by the remote measuring device can be displayed in the central control facility.
In order to operate a plurality of field devices from a central control facility, operating tools or operating instruments may have been developed that under a common user interface or user surface may make it possible to access the various field devices. The operating tools may provide an architecture, an environment or a frame, which may ensure, for example, a uniform appearance of displays and operating elements of field devices. By means of the uniform appearance, operation of the field devices can be simplified. The user interface may be able to simulate the operating device.
Integration of a field device in an operating tool may require a description of the user interface of the respective field device. As a rule, the user interface may be prepared individually for each field device. In the user interface device parameters, i.e. the device description, may be described in a description language so that the parameters can be interpreted by the operating tool. Because the description language may be standardised for the respective operating tool architecture, it may be possible to bring together the operation of field devices of various manufacturers under the common or shared operating tool.
As an overarching management system and as an overall management system, respectively the common operating tool can make operation of the field devices possible substantially independently of a particular field device manufacturer. The overarching management system or operating tool can be used, for example, in order to show and represent, respectively a connection between or among individual sensors, and may allow to gain an overview of a distribution of the field devices within the production plant. Examples of operating tools may be Emerson AMS, Siemens PDM or PACTware™.
For the integration of field devices of different manufacturers in the operating tool, the respective manufacturer of the field device may provide a user interface in the form of a file, which user interface may be adapted to the corresponding field device. Various technologies or technology concepts may have established themselves as an architecture for the operating tools; these technologies or technology concepts may have to be taken into account, by means of the description language, in the design of user interfaces for the respective operating tool. The availability of a user interface for the operating tool that may exist with a user can be relevant for a decision relating to the purchase of a field device.
For example, there may be the field device tool (FDT) system with device type managers (DTMs). In FDT technology binary files may be used as a user-interface description file in order to describe the user interface of the associated field device. The user-interface description file (DTM) may be equipped with the so-called FDT interface and may be read into the operating tool used (also referred to as the frame application or frame) in order to be able to address the field device via the operating tool. In this arrangement the FDT interface may define the connection channel between the frame application (e.g. PACTware™) and DTM.
Another concept may be pursued by means of the device description (DD) concept, the electronic device description (EDD) concept or the enhanced EDD (EEDD) concept. In DD, EDD or EEDD the user interface or the device description may be provided in an ASCII text that may be written with the use of a description language that in parts may be comparable to the programming language C. Therefore the user-interface description file may be a text file.
After having been read into the associated operating tool, the device description of the field device, which device description may be provided either as a binary file or as an ASCII file, may be used to represent the field device in a user interface within the operating tool or within the operating tool environment. By way of the interface or surface that may have been generated for the field device in the operating tool, the field device can be addressed by way of the uniform operating tool.
However, since the two different technology approaches by means of binary file and by means of ASCII file may exist, for manufacturers of field devices it may be necessary for each user interface concept to develop a device-specific device description for each individual field device. Each technology may have different development environments which in turn may require individual device descriptions. A device manufacturer may be compelled to provide several device descriptions for the same field device.
Although there may be conversion tools that automatically convert an existing device description based on EDD technology to a DTM based on FDT technology. However, since each technology may require its own device description in the form of a user-interface description file, the parameters and functions present in the device may have to be described several times and in a different manner. Such a different description may not be only associated with enormous expenditure of time and costs, but it may also be associated with the danger of providing faulty or inconsistent user interfaces in the different operating tools.
Furthermore, very considerable maintenance expenditure may be required if, for example, expansions of functions or extensions of parameters may be carried out in a field device or device, because these changes may also need to be incorporated in every user interface.
Each technology may offer different options in the design of the user interface. However, only the shared or commonly available functionality can be utilised in automatic conversion. Since the EDD and FDT/DTM technologies may use different parameters or functions, only the intersection (Schnittmenge) of the shared parameters that may be present can be converted from one device description technology to the other device description technology. It can thus, for example happen that DTMs that have been generated by means of conversion tools cannot exploit the technical possibilities provided by FDT technology because the functions or parameters may not be present in EDD technology.
Process automation technology may be intended to be used to allow controlling and monitoring of an industrial process. Operating tools can provide an overview of individual states of the process, as a result of which monitoring the industrial process is facilitated. In particular, field devices may be used to monitor such an industrial process, for example a production process or a conversion process.
Field devices can be used as sensors for acquiring process variables. Examples of common process variables that may be acquired during monitoring of a process may comprise physical values such as a fill level in a container, a pressure in a container, and a flow velocity of a medium through a pipe. Sensors may be used for acquiring, and in particular for measuring, the process variables. Examples of sensors may comprise fill level meters, flow meters, level meters, pressure meters, temperature meters etc.
As actuators, field devices can influence process variables, i.e. physical values. Actuators can support a control process or a regulating process. For example an actuator can influence the opening angle of a valve for controlling a flow quantity in a pipe. Valves or an OFF switch are examples of actuators.
In digital communications in processing (prozessverarbeitenden) systems or in field device systems, increasingly field devices and communication components of various manufacturers may be networked one with another. In such networked systems the communication components of the various manufacturers often also may have different performance characteristics.
Interconnecting several communication components to form a processing system can be referred to as a convoluted or a nested communication structure. In such field device systems the field devices may be operated by means of an operating tool connected to them.
The operating tool, of which there may be several entities in a large system arrangement, can communicate, via the nested communication structure, with a field device, in particular with a sensor and/or an actuator. A telegram, a packet, a notice or a message may be used for communication between the operating tool and a field device. Such a telegram may comprise a fixed telegram length, wherein the telegram length may be determined by the communication components, which components are arranged in the one field device system. Therefore, in a field device system, i.e. in the pool or network of field devices, an upper limit of the value of the telegram length may exist, wherein the telegram length may be determined by the component that permits, or can process, the shortest length relating to a telegram.
If the maximum possible telegram length may be used for exchanging telegrams, it may be ensured that the telegrams may not be rejected in the field device system due to excessive telegram length.
However, many device manufacturers may not state the maximum telegram lengths that can be processed in their components. Therefore the information relating to the maximum telegram length to be used in a field device system may be unknown. Consequently, it may be left to chance that the telegram length is set so that the components operate with the maximum possible telegram length.
If operation may be at a telegram length that may be shorter than the maximum possible telegram length, operation in the system may possibly be at too low speed of transmission.
There may be a need to provide effective transmission in field device systems.